The present invention relates, in general, to electronics, and more particularly, to methods of forming semiconductor devices and structure.
In the past, the semiconductor industry utilized various methods and structures to form switched capacitor step-up voltage circuits. One example of such a step-up voltage circuit was a charge-pump circuit such as a voltage doubler circuit. The voltage doubler generally used a capacitor that was alternately charged to a voltage and then coupled in series with the input voltage to power a load. In most applications, the voltage doubler used four transistors configured as two transistor pairs that were alternately switched to provide the desired charging of the capacitor. In some cases, the voltage doubler included a feedback loop that was used to set the value of the output voltage formed by the voltage doubler.
In some cases when the voltage doubler was used to regulate current, it was difficult to obtain good regulation, low pin count, and low cost with one single circuit charge-pump circuit. These three parameters generally were traded off against one another in order to achieve either low-cost, accurate regulation, or low pin count.
Accordingly, it is desirable to have a charge-pump circuit that has low pin count, that has a low cost, and that provides accurate regulation.
For simplicity and clarity of illustration, elements in the figures are not necessarily to scale, and the same reference numbers in different figures denote the same elements. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description. As used herein current carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor or a cathode or anode of a diode, and a control electrode means an element of the device that controls current through the device such as a gate of an MOS transistor or a base of a bipolar transistor. Although the devices are explained herein as certain N-channel or P-Channel devices, a person of ordinary skill in the art will appreciate that complementary devices are also possible in accordance with the present invention. It will be appreciated by those skilled in the art that the words during, while, and when as used herein are not exact terms that mean an action takes place instantly upon an initiating action but that there may be some small but reasonable delay, such as a propagation delay, between the reaction that is initiated by the initial action.